The present invention relates to a methacrylic resin composition and a film produced by molding the composition, and more particularly to a methacrylic acid ester resin composition containing a crosslinked acrylic acid ester elastomer and capable of providing a film having excellent properties such as impact resistance, transparency, weatherability, solvent resistance and plasticizer migration resistance, and a film made thereof. The present invention also relates to a methacrylic resin composition which can provide molded articles having a matt surface and a resistance to whitening owing to bending as well as the above-mentioned properties, and a film made thereof.
Methacrylic acid ester resins are particularly excellent in weatherability and transparency among plastics and have been used in various fields. For example, methacrylic resins have been widely used for the purpose of protecting various materials such as plastics, woods and metals from weathering by laminating the films thereof onto substrates of those materials. In order to improve the moldability into films and impact resistance of the methacrylic acid ester resins to be formed into the films or sheets for this purpose, it is usually practiced to disperse a rubber component into the methacrylic acid ester resins or to produce the methacrylic acid ester resins in the form of a graft polymer wherein the graft layer and the free polymer portion are softened, or in order to improve the impact resistance of the methacrylic acid ester resins, it is known to conduct a graft polymerization in multi stage to produce graft layer and free polymer having multi stage compositions, as disclosed in Japanese Patent Publication Kokoku No. 47-13371 and No. 50-9022. Also, in order to improve the impact resistance and the resistance to whitening owing to bending (hereinafter referred to as "flex whitening resistance" or "whitening resistance"), it is proposed to produce a graft polymer wherein the inner layer of a rubber polymer component has a glass transition temperature Tg of at least 10.degree. C., as disclosed in Japanese Patent Publication Kokoku No. 59-36645 and No. 59-36646.
However, methacrylic acid ester resins according to these conventional techniques are still poor in impact resistance and, therefore, even if films thereof are laminated onto base materials, the base materials cannot be protected against breaking. Further, if the amount of a rubber component included in the methacrylic acid ester resins is increased in order to raise the impact resistance, there arises a problem that the commercial value of the products is apt to be impaired due to lowering of transparency and plasticizer migration resistance.
On the other hand, molded articles of thermoplastic resins such as acrylic resins have generally a gloss surface, but molded articles having matt surface are preferred in some uses, e.g., interior material for vehicles, furniture, housing of electric appliances, wallpaper and building materials.
Conventional methods for delustering thermoplastic resins are roughly classified into (1) embossing or sanding the surface of articles and (2) adding an inorganic or organic matting agent to the resins. The method (1) has the advantage that the physical properties are scarcely lowered. However, the productivity is low and the processing cost increases and, in addition, the matting effect is insufficient. In many cases, the method (1) is not suitable for materials or articles subjected to a secondary processing. The method (2) is applicable to materials or articles subjected to a secondary processing without substantially lowering the productivity and control of the degree of matting is possible, but has a fatal defect that the physical properties are markedly lowered. In particular, in case of using an inorganic matting agent such as silica gel, physical properties such as impact resistance, strength, elongation and transparency are markedly lowered. As an organic matting agent, particularly polymeric matting agent, it is proposed to use a crosslinked polymer having an average particle size of 35 to 500 .mu.m obtained by suspension polymerization, as disclosed in Japanese Patent Publication Kokai No. 56-36535. The proposed matting agent shows decreased lowering of physical properties such as impact resistance, strength and elongation, but the matting effect is insufficient and the flex whitening resistance is poor. It is also proposed to deluster acrylic resins by using a matting agent in combination with a polyalkylene glycol, as disclosed in Japanese Patent Publication Kokai No. 9-272778. According to this method, the flex whitening resistance is improved, but physical properties such as impact resistance, heat resistance, strength and elongation are markedly lowered.
It is an object of the present invention to provide a methacrylic acid ester resin composition having excellent properties such as film formability, impact resistance, transparency, weatherability, solvent resistance and plasticizer migration resistance.
A further object of the present invention is to provide a methacrylic acid ester resin composition which can be stably formed by extrusion even under condition of a high drawing ratio to provide films having excellent impact resistance, transparency, weatherability, solvent resistance and plasticizer migration resistance.
A still further object of the present invention is to provide an acrylic resin film having excellent properties such as impact resistance, transparency, weatherability, solvent resistance and plasticizer migration resistance.
Another object of the present invention is to provide a thermoplastic acrylic resin composition which can provide molded articles such as films and sheets having a matt surface and having an improved flex whitening resistance without lowering impact resistance, heat resistance, tensile strength and other physical properties.
A still another object of the present invention is to provide a matt acrylic resin film having excellent flex whitening resistance, impact resistance and other physical properties.
These and other objects of the present invention will become apparent from the description hereinafter.